Dyax and Sigma-Tau Group Expand Agreement for KALBITOR (ecallantide) in Hereditary Angioedema

Additional Territories Include Countries in
Latin America and Southeast Asia

Expanded Agreement Includes $7M in Upfront
Payment, Up to $10M in Milestones

CAMBRIDGE, Mass.--May 31, 2011--(BUSINESS WIRE)--Dyax Corp.
(NASDAQ: DYAX) and Defiante Farmaceutica S.A., an
affiliate of the pharmaceutical group Sigma-Tau (Sigma-Tau),
announced today an expansion of their strategic partnership for
KALBITOR® (ecallantide) in the
treatment of hereditary angioedema (HAE) and other therapeutic
indications to include development and commercialization rights in
Latin America, excluding Mexico and the Caribbean, Taiwan,
Singapore and South Korea. Under their existing agreement, Defiante
holds these rights in Europe, North Africa, the Middle East,
Russia, Australia and New Zealand, with Dyax retaining rights to
KALBITOR in other territories, including the U.S., where it is
approved for the treatment of acute attacks of HAE in patients 16
years of age and older.

Dyax will receive an upfront payment of $7 million and is
eligible to receive up to $10 million in regulatory, approval and
reimbursement milestones. Consistent with their existing agreement,
Dyax is also eligible to receive sales milestones and royalties
equal to 41% of net sales of KALBITOR, less cost of goods sold.
Sigma-Tau is also responsible for costs associated with regulatory
approval and commercialization in their additional territories.

“The addition of these new territories to our strategic
agreement with Sigma-Tau is another important step in our ongoing
KALBITOR strategy,” stated Gustav Christensen, President and
Chief Executive Officer of Dyax Corp. “We will work with our
partner to maximize the global reach and commercial potential of
KALBITOR and position it to be the HAE treatment of choice
internationally.”

“The expansion of our agreement with Dyax speaks to the
success of this partnership, our continued dedication to KALBITOR
and our ongoing mission to provide treatment options to patients
with rare diseases,” said Mr. Ugo Di Francesco, Sigma-Tau
Group Executive Vice President and Chief Executive Officer.
“The addition of these territories to our agreement enhances
our global offerings in the specialty pharmaceutical business and
gives us the opportunity to provide an important new treatment
option to HAE patients in Latin America and Southeast
Asia.”

About HAE

Hereditary angioedema (HAE) is a rare acute inflammatory
condition characterized by episodes of severe, often painful
swelling affecting the extremities, gastrointestinal tract,
genitalia, and larynx. HAE is caused by low or dysfunctional levels
of C1 esterase inhibitor (C1-INH), a naturally occurring molecule
that inhibits plasma kallikrein, a key mediator of inflammation,
and other serine proteases in the blood. HAE is estimated to affect
1 in 10,000 to 1 in 50,000 individuals. Learn more at www.HAEHope.com.

About Dyax

Dyax is a fully integrated biopharmaceutical company focused on
discovering, developing and commercializing novel biotherapeutics
for unmet medical needs. The Company’s lead product,
ecallantide, has been approved under the brand name
KALBITOR® in the United States
for the treatment of acute attacks of hereditary angioedema (HAE)
in patients 16 years of age and older.

Dyax is commercializing KALBITOR in the United States
independently, and establishing strategic partnerships to develop
and commercialize ecallantide for the treatment of HAE in key
regions worldwide. Currently, Dyax has partnership agreements for
regions including Europe, Japan, Russia, the Middle East, Israel,
North Africa, Australia and New Zealand. The company is also
exploring other potential indications for ecallantide, either alone
or through partnerships, including drug-induced angioedema and
retinal vein occlusion-induced macular edema.

Ecallantide and other compounds in Dyax’s pipeline were
identified using its patented phage display technology, which
rapidly selects compounds that bind with high affinity and
specificity to therapeutic targets. Dyax leverages this technology
broadly through the Licensing and Funded Research Program (LFRP),
which has approximately 75 revenue generating licenses and
collaborations for therapeutic discovery, as well as for affinity
separations, diagnostic imaging, and research reagents. The success
of the Company’s LFRP royalty portfolio is illustrated by the
program’s advanced licensee pipeline that includes 17
candidates in clinical development. Of those candidates, four are
in Phase 3 clinical trials, four are in Phase 2 and nine are in
Phase 1.

About Sigma-Tau

Sigma-Tau is a leading, all Italian capital, international
pharmaceutical group that invests in the research, development and
marketing of innovative and effective treatments to improve patient
well-being and quality of life. Sigma-Tau Group has headquarters in
Pomezia (Rome, Italy), and subsidiaries in France, Switzerland, the
Netherlands, Belgium, Portugal, Germany, UK, India, US and Spain,
these two latter with a production plant. It has over 2400
employees and an extensive network of licensees worldwide.
Sigma-Tau was founded in Italy in 1957 and achieved a global
turnover of €673 million in 2010. Sigma-Tau invests on average
16% of its turnover in R&D, and employs approximately 400
researchers currently working on a significant discovery pipeline,
studying, through clinical and pre-clinical trials, 26 different
molecules, mostly (11) new and original, and 18 owned by the
Sigma-Tau Group. Therapeutic areas in which the company’s
research and development are focused include rare and neglected
diseases, oncology, immunology and Biotech. Sigma-Tau website:
www.sigma-tau.it.

Dyax Disclaimer

This press release contains forward-looking statements,
including statements regarding the prospects for therapeutic
benefits of KALBITOR for HAE. Statements that are not historical
facts are based on Dyax’s current expectations, beliefs,
assumptions, estimates, forecasts and projections about the
industry and markets in which Dyax competes. The statements
contained in this release are not guarantees of future performance
and involve certain risks, uncertainties and assumptions, which are
difficult to predict. Therefore, actual outcomes and results may
differ materially from what is expressed in such forward-looking
statements. Important factors which may affect the prospects for
therapeutic benefits of KALBITOR for HAE include the risks that:
others may develop technologies or products superior to KALBITOR or
that are on the market before KALBITOR; KALBITOR may not gain
market acceptance; Dyax is dependent on the expertise, effort,
priorities and contractual obligations of third parties in the
manufacture, marketing, sales and distribution of KALBITOR; and
other risk factors described or referred to Item 1A, “Risk
Factors” in Dyax’s most recent Annual Report on Form
10-K and other periodic reports filed with the Securities and
Exchange Commission. Dyax cautions investors not to place undue
reliance on the forward-looking statements contained in this
release. These statements speak only as of the date of this
release, and Dyax undertakes no obligations to update or revise
these statements, except as may be required by law.

Dyax, the Dyax logo and KALBITOR are registered trademarks of
Dyax Corp.